In the art of making tire components, especially tire treads, silica has been employed as a filler to provide, among other benefits, advantageous wear characteristics. The silica is employed in conjunction with a silica coupling agent that chemically links the silica to the rubber. For example, mercaptosilanes have been employed as coupling agents whereby the mercapto unit reacts with unsaturation within the rubber and the silane unit reacts with the surface of the silica particle through a condensation reaction. The prior art, such as U.S. Publ. No. 2004/0152811, teaches that strong bases, such as diphenyl guanidine, can promote this condensation reaction and lead to improved results. These strong bases, however, also act as accelerators for sulfur curing of the rubber, and therefore the use of these strong bases must be carefully tailored so as not to deleteriously impact cure properties.
The prior art also proposes the use of nicotinamide as a cure accelerator during sulfur curing of vulcanizable compositions. For example, U.S. Pat. No. 5,504,137 teaches the addition and mixing of nicotinamide, together with sulfur at temperatures or mixing energies that are consistent with mixing conditions where curative is present (i.e., productive mixing). The prior art does not, however, teach or appreciate any benefits that may be associated with the mixing of nicotinamide in a masterbatch or non-productive mixing step.